It was found that there are no existing mixing machines; except for the design herein disclosed, for thoroughly mixing a resin binder compound with aggregates to produce a building material of controlled consistency. Prior art machines such as cement mixers, stirrers and machines employing simple screw conveyors, do not coat each individual particle of aggregate and can not adequately coat dust and fines with the resin compound. Furthermore, such existing machinery requires a long mixing time and is not adaptable to producing high volume, continuous-flow, quality-controlled aggregate products acceptable as structural building material.